(Open access full text) - The aim of this article is to analyze the French Social Security System (SSS) within the framework of the Economics of Convention (EC). From this perspective, we consider that the SSS is permeated by three competing con-ventions: an anticapitalist convention, a solidaristic convention, and a liberal convention. We use conventions as ideologies in order to address conflict and power in the context of EC. The French SSS is not the outcome of a consensus but of conflicts. An empirical analysis of historical documents and political de-bates during the sessions of the French National Assembly is mobilized in order to examine two key moments of controversy in 1949 and 1967